How Effective is Geophysical Survey? A Regional Review

Geophysics is such an accepted part of British archaeology that its effectiveness seems obvious. Yet if there is no reason to doubt the benefits of geophysics why do some experienced archaeologists use it so rarely and why is it little used in some countries which, in other ways, have highly developed professional archaeology services? There are, often cheaper, alternatives for archaeological survey Yet since the performance of different survey methods has rarely been studied systematically there is no objective basis on which to test which choices best meet archaeologists' needs. Moreover the geophysicists' understandable desire to present successful rather than unsuccessful surveys, and to discuss results in geophysical rather than archaeological terms, makes such assessment more difficult. Thus although geophysical surveyors have strong grounds to claim that their work benefits archaeology, those who pay for survey can reasonably ask that these benefits be clarified, quantified where possible, and compared with alternatives, such as aerial photography or surface artefact survey, so that they can make the best choices about its use. This paper summarizes a study of all the geophysical surveys carried out in the northwest of England before 2006. The study assessed the performance of geophysical surveys in archaeological terms and was centred on a detailed analysis of 35 sites for which there is good comparative excavation data or which have particularly illustrative case histories. The study concludes that, despite the doubts in this area, geophysics serves archaeologists well and provides greater certainty in both identifying where sites exist and where they do not exist than has been generally assumed. It therefore deserves more extensive and more rational use. Geophysics is, however, being underused because, although abundant, surveys are formulaic and commercial surveyors are rarely able to fit methodologies to sites by a programme of reflective project development. Thus, although currently effective, geophysics might be even more so if surveyors had the time and resources to do this and to answer more complex and specific questions. The paper considers how these findings relate to the use of geophysical survey in other countries. Copyright (C) 2009 John Wiley & Sons, Ltd.